1. Field of the Invention
The present invention relates to a three-dimensional shape measuring apparatus which measures a three-dimensional shape of a target object.
2. Description of the Related Art
An example of means for obtaining three-dimensional shape information on an object by image analysis includes a method of analyzing a deformation amount of the optical pattern changed according to the three-dimensional shape of the target object by projecting an optical pattern onto a target object existing in a predetermined imaging visual field. A light-section method, a spatial encoding method, a fringe analysis method can be cited as a typical example. These methods are based on the principle of triangulation. Among others, for the fringe analysis method, there are proposed many techniques such as spatial fringe analysis and temporal fringe analysis, and the fringe analysis method is known as a technique in which high measurement accuracy is obtained.
In these techniques, usually an area camera is used to read the target object onto which the optical pattern is projected. However, when the area camera is used, because the target object does not fit into one imaging visual field, it is necessary that the area camera be moved in both the lengthwise direction and the crosswise direction to take the one imaging visual field while the one imaging visual field is divided into plural portions, which results in the problem that the imaging time is lengthened.
In order to solve the problem, conventionally there is proposed a three-dimensional shape measuring method in which a line sensor is used instead of the area camera (refer to, for example, Japanese Patent Laid-Open Nos. 2002-286433 and 2004-117186 and Fujigaki, et al., “Parallel optical grating projection method in continuous object shape measurement using plural line sensors” Proceedings on fall semestrial conference of the Japan Society for Precision Engineering pp. 1061-1062, 2004). This measuring method is performed by the following steps. The target object onto which the optical pattern is projected is taken by the line camera, the phase of the projected optical pattern is shifted by moving the target object, the target object onto which the optical pattern having shifted phase is projected is taken by another line camera; the above processes are repeated plural times, and the optical patterns included in the plural taken images are analyzed to measure the three-dimensional shape based on the temporal fringe analysis method (phase shift method).
In a three-dimensional shape measuring apparatus proposed in Japanese Patent Laid-Open No. 2004-117186, the three-dimensional shape is measured by the following method. The target object onto which the optical pattern is projected is taken separately by two line cameras placed at different positions, and the three-dimensional shape is measured from the two taken images based on the stereo method.